The present invention relates to optical readers such as a bar-code scanner and an image scanners.
Optical readers of the above-mentioned type have the following construction. For instance, in the case of a barcode scanner, it includes a main body of a casing which accommodates various members such as a light emitting element, a light receiving element, optical fibers serving as a light channeling means, and an electrical processing circuit. The forward end of the main body of the casing is closed by a metal cylindrical cap. A light passage hole is formed in the metal cap, and a ball lens is fitted in the hole.
With this construction, when a beam is emitted from the light emitting element, it transmits through the ball lens to be projected onto a bar code to be read. The beam reflected by the bar code transmits through the ball lens to be received by the light receiving element. The light receiving element generates a signal which is then analyzed by the electrical processing circuit. The bar code is read in this manner.
During the manufacture of such a conventional optical reader, a ball lens is inserted into a light passage hole already formed in a metal cap by grinding. While the inserted ball lens is spinning, a tip portion of the cap is caulked so that the ball lens fits into the hole of the cap and held therein. This caulking process, however, involves a risk that the ball lens may be broken. In such cases, high cost is inevitably incurred in the production of the cap assembly.
In order to avoid this risk, proposals have been made for resin molding of caps.
One of such proposals will be described with reference to FIG. 2 showing the cap portion of a conventional optical reader. A cap 6 is formed by a resin molding method employing a first mold part 3 having a body portion 1 formed as a part of a sphere and a cylinder portion 2 formed integrally at an end of the body portion 1, as well as a second mold part 3 having a tip formed as a tapering portion 4. Although not shown, besides the first and second mold parts 3 and 5, another mold part is used to shape the outer surface of the cap 6.
When the cap 6 is formed in this way, a mounting recess 7 having a spherical inner surface and a bore 8 continuing from the recess 7 are formed in their respective portions of the tip of the cap 6. In order to allow the formation of a suitable draft angle, the bore 8 has a configuration in which its inner diameter increases from its inward end toward its outward end.
After the cap 6 has been formed, it is mounted on a main body 9 of the casing, indicated by one-dot-chain lines in FIG. 2, in such a manner that the cap 6 closes an opening 10 at the forward end of the main body 9. Subsequently, while the cap 6 is slightly deformed, a ball lens 11 is fitted into the mounting recess 7, thereby completing the assembly of the optical reader. Thus, when a cap 6 is formed by the proposed resin molding method, it is possible to prevent the risk of the ball lens 11 being damaged during assembly.
However, the above-described proposal entails the following drawback. Since the first mold part 3, which is used to form the bore 8 as well as the mounting recess 7 for fitting therein the ball lens 11, must have the spherical body portion 1 and the cylinder portion 2 integral at one end thereof, the first mold part 3 can be machined only with difficulty. This makes the preparation of the entire mold expensive. Thus, the proposal fails to manufacture a cap assembly without incurring high production cost.